In digital television broadcasting in Europe, a common interface (CI) is being conventionally used in order to achieve a system (conditional access system (CAS)) that exclusively receives scrambled broadcasting. A plurality of streams has become handleable with the common interface (version 1.4), and a CI module is supplied with one multiplexed transport stream (TS) obtained by multiplexing a plurality of TSs.
For example, Patent Document 1 discloses a digital broadcasting receiving system capable of transmitting/receiving one composite stream finely to/from external devices. The composite stream is obtained by combining a plurality of streams.
Incidentally, the receiving device that receives a plurality of streams includes a first in first out (FIFO) unit in order to avoid collision that may occur in a case of multiplexing a plurality of TSs into one multiplexed TS. In addition, in order to suppress the bit rate of a multiplexed TS, the receiving device converts unnecessary packets, included in the TSs to be multiplexed, into null packets. The receiving device replaces the null packets with valid packets included in other TSs.
Here, in order to suppress the overall bit rate of the multiplexed TS, regular null packets are discarded. Therefore, the original number of the null packets is not ensured. As a result, the arrival time of the packets arriving at a latter decoding unit may be quickened, or delayed because a larger number of packets of other TSs are inserted than the number of the actual null packets that have existed.